The present invention relates to novel cyclopolymethylenefluoran compounds which are colorless or substantially colorless, but are instantaneously colorable when brought into reactive contact with suitably sensitized sheets containing an acidic electron-acceptor such as the protic acids, e.g., organic acids, phenolic acids, phenols, diphenols, phenolic resins of the novolak type, and aprotic acids, e.g., Lewis acids, acid clays, etc., or mixtures of these materials. These properties and others disclosed hereinafter make the compounds of this invention suitable for use in various types of carbonless pressure-sensitive copy papers, thermally-sensitive imaging papers, thermally-sensitive imaging transparencies for overhead projection screens and other copy or image applications.
A number of chemical compounds are disclosed in the prior art to be useful as color-precursors when brought into contact with acidic electron-acceptors. Included in the suitable compounds are the 6-dialkylamino fluoran compounds having alkyl groups in the 1,2 and/or 3 position, the preparation of which and/or use in pressure sensitive transfer papers are disclosed in U.S. Pat. Nos. 3,442,908, issued May 6, 1969 to Michio Orita et al., 3,637,757, issued Jan. 25, 1972 to Chao-Han Lin, 3,641,011, issued Feb. 8, 1972 to Chao-Han Lin et al., and 3,713,863, issued Jan. 30, 1973 to Chao-Han Lin et al. None of these prior art patents disclose fluoran compounds which include a cyclopolymethylene group on the fluoran structure. U.S. Pat. No. 3,901,918, issued Aug. 26, 1975 to Koichi Koga et al., discloses 2-amino fluoran compounds with a tetramethylene group attached to the benzene ring at the 3,4 position.
This application is related to commonly assigned U.S. application Ser. No. 461,860, filed Apr. 18, 1974, now U.S. Pat. No. 3,929,825.